Pathogens are causative agents of disease. Food-borne pathogens are pathogens, whether infectious or toxic, that enter the body through the consumption of food. These pathogens which include viruses, bacteria, parasites, toxins, metals, and prions, can lead to illness, hospitalization, or even death in humans (Mead et. al, 1999). The Centers for Disease Control and Prevention have estimated that food-borne diseases cause approximately 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States each year (Mead et. al, 1999). Mead et al. (1999) have also projected that bacteria cause 72% of the deaths that are attributable to foodborne transmission. Some bacterial species that are of concern are Salmonella, Campylobacter jejuni, Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, Clostridium perfringens, and Cyclospora cayetanensis. 
Food matrices have complex structures consisting of carbohydrates, proteins, fats, oils, minerals, vitamins, etc., not to mention the different preservatives that are added in order to ensure shelf-life. Consequently, the sampling and analysis of foods for the presence of pathogens offer many challenges. Swaminathan and Feng (1994) noted that these result from the extensive variations in physical characteristics and chemical compositions of foods, the extent of food processing (raw foods to nearly sterile foods packed in hermetically sealed containers), the microorganisms present in foods, and the degree of sublethal injury inflicted on the bacteria present in foods.
Because foods comprise differing organic and inorganic molecules in differing concentrations, pathogens may adjust their metabolism accordingly for survival. This response is not beneficial if the goal is to rapidly detect pathogens because there may be some surface antigen or modification that may or may not be expressed so a preenrichment step is often performed in order to resuscitate the injured or stressed bacteria to resume its normal metabolism. A preenrichment step not only salves bacteria but can also serve to increase the number of pathogenic microorganisms that may be outnumbered from the indigenous microflora in a matrix (Swaminathan and Feng, 1994, Stevens and Jaykus, 2004).
The use of culture enrichment and selective plating are good, quality, conventional tools to identify specific pathogens, but they are very lengthy and may take up to four days to obtain even preliminary results (Stevens and Jaykus, 2004). While a confirmation of whether a food sample is pathogen-free is being waited for, a consumer may have already consumed it. Therefore, there needs to be some way of rapidly separating and concentrating pathogens from a food matrix for their detection.
Separation and concentration are important because they offer advantages of facilitating the detection of multiple bacterial strains, removal of matrix-associated reaction inhibitors, and providing ample sample size reductions to allow for the use of smaller media volumes (Stevens and Jaykus, 2004). A battery of tests exists that may be used for the detection of bacteria. A direct epifluoresent filter technique (DEFT), which combines enumeration and microscopy, has been used to detect bacteria (Hugo and Russell, 1998). This technique concentrates bacteria from a large sample volume using a polycarbonate filter. The bacteria are then stained with acridine orange for enumeration (Deisingh and Thompson, 2002). Bioluminescence for adenosine triphosphate (ATP) has been used in the analysis of fresh meats and other foods for microorganisms (Swaminathan and Feng, 1994). Immunological approaches have been used for the detection of bacteria which use enzyme-linked immunosorbernt assay (ELISA) and immunomagnetic separation (Deisingh and Thompson, 2002).
These methods usually cannot be used directly with foods due to the presence of interfering materials and to the low numbers to target cells (Payne and Kroll, 1991). Particularly, when using microfluidic-based sensors, samples have to be almost particulate or colloidal free for successful pathogen detection. When particulates are present, they may alter the metabolism of pathogens and/or cause a false positive or negative result. Thus, there is a need in the art for sequestering pathogens from food matrices in a way that provides a detectable amount of bacteria in a relatively particulate- or colloidal-free sample.
The background information above is provided to set forth the nature of some of the problems addressed by the present invention. Inclusion of a reference or work by others in this section is not an admission that such work or reference is prior art to the present invention.